Stereoselective Synthesis of Eight-Membered Cyclic Ethers by Tandem Nicholas Reaction/Ring-Closing Metathesis: A Short Synthesis of (+)-cis-Lauthisan

Cis-2,8-disubstituted oxocanes and the parent unsaturated precursors were prepared from the corresponding Co2(CO)6-cycloalkynic ethers. Key steps in such synthesis were the ether linkage formation by intermolecular Nicholas reaction, RCM of the suitable acyclic dienyl ether and montmorillonite K-10 induced isomerization of the complexed cycloalkyne. A short synthesis of (+)-cis-lauthisan taking advantage of the developed methodology is described.